Connector having improved contacts with fusible members

ABSTRACT

An electrical connector includes a connector body, a plurality of cores and a plurality of electrically conductive contacts disposed in the cores of the connector body. Each of the contacts includes a fusible member attached thereto. Each of the fusible members includes an intermediate portion and two support members disposed on opposite sides of the intermediate portion. The support members are arranged to hang down below a tail portion of the contacts.

This application is a Continuation application of prior application Ser.No. 10/876,740, filed Jun. 28, 2004, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrical connectors and morespecifically, the present invention relates to connectors having aunique arrangement of contacts or terminals having a fusible memberattached thereto, that allows for much higher coplanarity whilesimplifying the connector manufacturing and assembly procedures.

2. Description of the Related Art

Electrical connectors are used to place electrical devices, such asprinted circuit boards, in communication with one another. An electricalconnector may be thought of as having two portions, one portion of whichconnects to a first electrical device and the second portion of whichconnects to a second electrical device to be put into communication withthe first device. To connect the two devices, the two portions of theelectrical connector are mated together.

Each portion of the connector includes one set of contacts or terminalsadapted to communicatively couple to an electronic device and a secondset of contacts or terminals adapted to matingly couple to the otherconnector portion. This can be readily accomplished by designating oneportion of the connector as having “male” contacts or terminals adaptedto couple to the other connector portion's “female” contacts orterminals. Regardless of the specifics of the design of the contacts orterminals, the two connector portions should be adapted to be easilyconnected and disconnected from each other to respectively electricallylink and unlink the electrical devices to which they are connected.

Accordingly, each connector portion is fixedly connected to anelectronic device through its remaining set of contacts or terminals.The contacts or terminals may be removably or permanently connectable tothe electrical device; however, it is usually desired that the connectorportion be secured to the electrical device through some physicalmechanism. Typically, the connector portions are secured to electricaldevices by fusing the contacts or terminals to contact pads or the likeformed on the electrical device.

Recently, there has been a trend toward miniaturization of mostelectrical devices. As electrical devices become smaller and morecomplex, the electrical connectors used with these devices must alsobecome smaller and must be able to accommodate the more complex devices.One problem with miniaturized electrical connectors arises from theincreased precision of placement necessary to produce the properpositioning and connection of the connector contacts or terminals ontothe device. This problem is exacerbated by the ever increasinginput/output (I/O) density requirements demanded of the progressivelysmaller electrical connectors by increasingly miniaturized electricaldevices. With increased pin counts (e.g., greater number of terminals)in each connector, it becomes more and more difficult to maintaindesired levels of co-planarity while maintaining contact of all of theterminals to a substrate or PCB.

One means of addressing the need for increased I/O density is to providean arrayed connector. Such a connector can provide a high-densitytwo-dimensional array of contacts or terminals for interfacing with anelectrical device. However, arrayed connectors present attachmentdifficulties regarding connection to devices (i.e., circuit boards orsubstrates) since most of the contacts or terminals must necessarily bepositioned in the interior of the two-dimensional array area and areaccordingly difficult to align upon connection, visually inspect, and/orrepair.

One attempt to provide a high-density electrical connector interface hasbeen to use a ball grid array (BGA). The BGA offers the advantages of aprecisely formed high-density array of contacts or terminals availableto interconnect with a substrate. The use of a BGA is thought toovercome conventional problems with co-planarity (e.g., to maintainco-planarity at about 0.004″, for example) and to ensure that allcontacts or terminals are securely soldered to pads on a PCB when theconnector is mounted and reflowed to the PCB.

However, the use of a BGA has many disadvantages. First of all, the useof solder balls greatly complicates the connector manufacturing processbecause an additional reflow step is required and the use of specialequipment is also required. In addition, either the connector bodyand/or contacts or terminals must be modified to include recesses orsolder ball holding structures, or special assembly equipment must beused to hold the solder balls in place until the solder balls can bereflowed to be connected to the tails of conductive contacts orterminals provided in the housing of the connector. After the solderballs have been reflowed a first time so as to be attached to the tailsof the contacts or terminals, the entire connector must be reflowedagain so that the solder balls can make the necessary electrical andmechanical attachments to conductive pads on a PCB upon which theconnector is being mounted. A further problem may occur when the solderballs are attached to gold-plated tail portions of the contacts orterminals, during which process the gold of the tail portions of thecontacts or terminals can mix with the tin/lead of the reflowed solderball which can cause problems with gold embrittlement.

In addition to the above-described problems, variations in thedimensions and/or placement of solder balls at the interface can lead toan uneven or non-coplanar interface and intermittent or poor electricalcontact. Also, the presence of oversized or extra solder balls presentin the connector interface, or the uncontrolled spreading of the solderballs during the multiple reflow steps can result in shorted connectionsand degraded connector performance. In addition, the tails of thecontacts or terminals are inserted and attached at different depthswithin the various solder balls so as to create problems withco-planarity. Furthermore, the solder joints created by the solder ballsbetween the contacts or terminals and the pads on the PCB is not asreliable and may not withstand twisting or distortion of the connectorbody which may occur. That is, the solder joints created using solderballs are not as flexible and may not withstand the stresses applied tothe joints when the connector body bows, twists or is distorted inshape.

One alternative to the use of a BGA is described in U.S. Pat. No.6,679,709, in which circular columns of solder 6 are used instead ofsolder balls. The circular columns of solder 6 have an elongatedcylindrical bar-shaped configuration and in fact are formed by cuttingpieces of solder wire. These circular columns of solder 6 are insertedbetween a pair of bar-like pieces 12 which are then bent to allow claws13 to grip and hold the solder 6 on the respective terminal or pin 5such that a longitudinal axis of the circular column of solder 6 isperpendicular to a mounting plane of a PCB or circuit board to which thesolder 6 and connector is to be attached. Thus, the solder holdingassembly (elements 12, 13, 14) must be arranged perpendicular to themain body 10 of the contact or terminal 5, which complicates themanufacturing and assembly of the contacts or terminals 5 in theconnector body. In addition, because the circular columns of solder 6may have different lengths and may be mounted at different positionswith the solder holding assembly (12, 13, 14) of each terminal, manyproblems with co-planarity may result. Thus, this complicated tailassembly of the contacts or terminals 5 makes manufacturing and assemblymore difficult and may cause rather than solve co-planarity problems.

Another alternative is the use of solder-bearing contacts in which thesolder has been crimped to the contacts, as shown in U.S. Pat. No.4,597,628, for example. In this patent, a solder bearing edge clip 10has arms 15, 16 with arcuate fingers 18, 19 having solder wires 30attached thereto. The attaching process involves inserting solder wires30 into openings at the ends of the fingers 18, 19, closing or crimpingthe fingers to close the openings so as to indent the solder wires 30 asshown in FIGS. 3 and 12. The solder is then melted to attach the arms15, 16 or 75, 76 to the pads 12 of the substrate 11 as seen in FIGS. 4and 13. In most of the embodiments shown in this patent, the solder wireis spaced from the outer surfaces of the fingers 18, 19 or 68, 69because the fingers 18, 19 or 68, 69 must be able to reliably hold thesubstrate. FIGS. 11A and 11B show an embodiment where the solder wire71′ projects very slightly from the finger ends so that when thesubstrate is inserted, the solder wipes across the contact pad 12 toimprove the resulting solder joint. However, with this structure, thereis no way to control how far the solder projects from the finger endsand thus, no way to ensure that the substrate is reliably held in thearms. If the finger ends are crimped too much, excessive solder willproject from the finger ends and it may not be possible to reliably holdthe substrate between the fingers. If the finger ends are not crimpedenough, the solder will not project from the finger ends. In addition,if fingers 18, 19 or 68, 69 are bent, twisted or having varyingdimensions due to manufacturing tolerances, there may be an air gapbetween the pads 12 and the fingers 18, 19 or 68, 69 and solder. Thisair gap may not be filled by the solder during reflow because the soldermay not be sufficiently wicked or moved toward the pad during reflow.Thus, there may still be problems with reliably forming or solderingelectrical connections between fingers 18, 19 or 68, 69 and the pads 12.

In fact, this is one of the most significant problems with electricalconnectors in which conductive contacts or terminals are to be joined toconductive elements on a substrate. Because of twisting or flexing ofthe connector or variations in size, shape, or arrangement of thecontacts or terminals in a connector body, an air gap may exist betweenthe contact or terminal and a conductive pad to which it is to beattached before the reflow process is performed. The current designs andarrangements of contacts or terminals in the connectors do not providefor a consistently reliable solution for eliminating the air gap duringreflow, and do not ensure that each contact or terminal is securelyconnected to the conductive pad on a substrate to which the connector ismounted.

SUMMARY OF THE INVENTION

In order to overcome the unsolved problems of the prior art describedabove, preferred embodiments of the present invention provide anelectrical connector that allows for much greater co-planarity to beachieved and also allows for a much more reliable reflow process to beperformed to reliably connect a connector to a substrate.

According to a preferred embodiment of the present invention, anelectrical connector includes a connector body, a plurality of contactsarranged in the connector body, each of the plurality of contacts havinga tail portion with a fusible member attached thereto, wherein each ofthe fusible members includes an intermediate portion and two supportmembers disposed on opposite sides of the intermediate portion, and thetwo support members extend below the tail portion of the contact.

It is preferred that each of the two support members extends below thetail portion of the contact by a distance of about 0.004 inches to 0.014inches, and that an outer periphery of each of the two support membersis greater than an outer periphery of the tail portion of the contact.

Furthermore, it is preferred that the two support members are arrangedto wick up the tail portion of the contact in a direction toward theconnector body during a reflow process. When this happens, the portionsof the support portions that previously hung below the bottom tip of thetail portion moves up the tail portion such that there is no longer anyportion of the fusible member that hangs down below the bottom tip ofthe tail portion. As a result, each contact or terminal and the entireconnector is able to drop down such that the bottom tip of the tailportion is located very close to the substrate and is reliably attachedto the substrate. This allows the connector to have much greaterco-planarity and a much more reliable reflow process.

The configuration and arrangement of the contact or terminals hasadditional unique features. It is preferred that the contact or terminalhas a key hole defined by a first horizontally extending arc and twovertically extending arcs, such that the intermediate portion of thefusible member is fitted within the key hole. More specifically, theintermediate portion of the fusible member fills the keyhole defined bythe first horizontally extending arc and the two vertically extendingarcs. This allows the fusible member to be quickly and reliably attachedto the contact or terminal and eliminates a reflow step required withBGA connectors.

The contacts or terminals may also include a solder stop portion locatedat a medial portion thereof. In addition, the tail portions of thecontacts are substantially straight and do not include a right angleportion as is required with some conventional contacts described above.

The contacts or terminals may also include wings for engaging a core ofthe connector body to maintain a uniform distance between the tailportion of the contacts and the connector body.

Also, the contacts or terminals may include wedges for engaging a sidewall of a core of the connector body in order to fix the contact in theconnector body.

Furthermore, the contacts or terminals may include lead-in portionshaving coined edges arranged to position the contacts in the connectorbody.

The contacts or terminals may also include bumps for positioning thecontacts within the connector body.

The fusible member also has unique features in addition to thosedescribed above. Each of the two support portions has one of asubstantially flat bottom surface, a substantially rounded bottomsurface, a substantially spherical bottom surface, a substantiallyconical bottom surface, a substantially rectangular bottom surface and asubstantially square bottom surface. Also, the intermediate portion andthe two support portions are integral and unitary, and the supportportions are located on opposite sides of the tail portion of thecontact.

Each of the two support members extends from the intermediate portionand is larger than the intermediate portion. The two support memberspreferably have substantially the same size and shape.

It should be noted that the above-described unique arrangement andconstruction of the fusible member attached to the contacts or terminalsof a connector can be applied to any type of connector including aboard-to-board mezzanine connector, a differential pair array connector,a single ended array connector, an edge card connector, a right angleconnector, a wafer for use in a backplane connector system, a connectorfor use with an IC chip such as a microprocessor chip (e.g., a Pentium®socket) and any other type of connector.

Another preferred embodiment relates to a connector assembly in which aconnector according to the preferred embodiments described above isattached to a substrate, such as a PCB. In such a structure, the uniquecontacts or terminals with attached fusible members are arranged to bemounted on and attached to conductive elements on the substrate.

A further preferred embodiment of the present invention provides amethod of forming a connector including the steps of providing a contacthaving a tail portion, inserting a fusible member into the tail portion,pressing edges of the fusible member such that an intermediate portionand two support portions of the fusible member are formed such that thetwo support portions extend down below a bottom tip of the tail portionof the contact. The resulting intermediate portion, two support portionsand the arrangement thereof on the tail portion of the contactpreferably have the features described above with respect to the otherpreferred embodiments of the present invention described above.

Yet another preferred embodiment of the present invention provides amethod of mounting a connector to a substrate, in which the connectormanufactured according to the method described in the precedingparagraph, is positioned above a substrate such that a respective one ofthe contacts is located directly above a respective one of a pluralityof conductive elements formed on the substrate, and reflowing theconnector and substrate such that the fusible members are melted causingthe support portions of the fusible members to wick up the contacts awayfrom the tail portions, resulting in the contacts and the connectordropping down toward the substrate, such that the contacts areelectrically connected to the conductive elements formed on thesubstrate.

Other features, elements, steps, characteristics, and advantages of thepresent invention will become more apparent from the following detaileddescription of preferred embodiments of the present invention withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an isometric view of a connector according to a preferredembodiment of the present invention.

FIG. 1B is an end view of the connector of FIG. 1A.

FIG. 2A is an end view of a contact or terminal according to anotherpreferred embodiment of the present invention.

FIG. 2B is a side view of a contact or terminal according to thepreferred embodiment of the present invention shown in FIG. 2A.

FIG. 3 is an assembly view of a plurality of contacts or terminals on acarrier strip for use in preferred embodiments of the present invention.

FIG. 4A shows a first assembly step for joining a fusible member to atail of a contact or terminal wherein a fusible member is positioned atan opening in the carrier strip just below the tails of the contacts orterminals.

FIG. 4B shows a second assembly step for joining a fusible member to atail of a contact or terminal wherein the fusible member is inserted inthe tails of the contacts or terminals.

FIG. 4C shows a close-up detailed view of a fusible member having beenjoined to the tail of a contact or terminal as a result of the stepshown in FIG. 4B being performed;

FIG. 4D shows a third assembly step for joining a fusible member to atail of a contact or terminal wherein the fusible member is pressed atopposite ends thereof;

FIG. 4E shows a close-up detailed view of the resulting support portionsformed by the step of pressing the opposite ends of the fusible memberas a result of the step shown in FIG. 4D being performed;

FIG. 4F shows a close-up detailed view of the resulting intermediateportion filling the arc portions of the tail of the contacts orterminals as a result of the step shown in FIG. 4D being performed;

FIG. 4G shows a detailed section view of the fusible member bearingtails of the contacts or terminals as a result of the step shown in FIG.4D being performed;

FIG. 4H shows a detailed side view of the fusible member bearing tailsof the contacts resulting from the step shown in FIG. 4D;

FIG. 5A is an end view of a connector according to a preferredembodiment of the present invention being mounted on a PCB before areflow process.

FIG. 5B is a side view of a connector according to a preferredembodiment of the present invention being mounted on a PCB before areflow process.

FIG. 6A is an end view of a connector according to a preferredembodiment of the present invention being mounted on a PCB after areflow process.

FIG. 6B is a side view of a connector according to a preferredembodiment of the present invention being mounted on a PCB after areflow process.

FIG. 7A is a schematic view of a conventional connector having tailportions of the contacts or terminals aligned with pads of a PCB beforea reflow process for joining the connector to the PCB is performed.

FIG. 7B is a schematic view of a conventional connector having the tailportions of the contacts or terminals being attached to a PCB after areflow process for joining the connector to the PCB is performed.

FIG. 8A is a schematic view of a connector according to a preferredembodiment of the present invention having fusible member bearing tailsbeing placed on a PCB before a reflow process for joining the connectorto the PCB is performed.

FIG. 8B is a schematic view of a connector according to a preferredembodiment of the present invention having fusible member bearing tailsbeing connected to a PCB after a reflow process for joining theconnector to the PCB is performed.

FIG. 9 is an isometric view of a mezzanine connector according to afurther preferred embodiment of the present invention, which includesfusible member bearing contacts or terminals of preferred embodiments ofthe present invention.

FIG. 10 is an isometric view of an edge card wafer with fusible memberbearing contacts or terminals of the preferred embodiments of thepresent invention for use in a backplane connector according to anotherpreferred embodiment of the present invention.

FIG. 11A is a side view of a connector for an IC chip according toanother preferred embodiment of the present invention, which includesfusible member bearing contacts or terminals of preferred embodiments ofthe present invention.

FIG. 11B is a top view of the connector of FIG. 11A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the drawings.

FIG. 1A is an isometric view and FIG. 1B is an end view of a connector10 according to a first preferred embodiment of the present invention.The connector 10 includes a body 12 that is preferably made of aninsulating material such as plastic, a plurality of cores (not shown inFIGS. 1A and 1B, but shown as element 14 in FIG. 9 which illustratesanother preferred embodiment of the present invention) formed in theconnector body 12 for receiving a plurality of contacts, and a pluralityof contacts or terminals 20 inserted into the cores and held in the body12. It should be noted that the connector 10 is shown in FIGS. 1A and 1Bin a state before being reflowed to be attached to a substrate such as aPCB.

As seen in FIGS. 1A and 1B, each of the contacts or terminals 20includes a fusible member 40 that is fixed to a tail portion 22 of thecontact 20. It should be noted that the fusible member 40 can preferablybe a conductive material that can be melted by a reflow process, such assolder or other suitable metal. In addition, the fusible member 40 canbe a flux coated solder material member or a flux core solder wire.Preferred embodiments of the present invention will be described withreference to solder wires constituting the fusible member 40, but thisis in no way limiting of the present invention.

Each fusible member 40 has two support portions 40 a, 40 b which areconnected to each other by an intermediate portion 40 c. The two supportportions 40 a, 40 b are disposed opposite to each other and spaced fromeach other by a distance that is equal to a length of the intermediateportion 40 c. The two support portions 40 a, 40 b may preferably havesubstantially flattened bottom surfaces as shown in FIG. 1B. However,the bottom surfaces of the support portions 40 a, 40 b may also haveother shapes such as rounded, spherical, conical, square, rectangular,and other suitable shapes.

It is preferred that the support portions 40 a, 40 b be formed such thatan outer periphery of each of the support portions 40 a, 40 b is greaterthan an outer periphery of the tail portion 22 of the contact orterminal 20, as seen in FIGS. 1A and 1B, for example. This feature alongwith other unique features of the arrangement of the fusible member 40attached to the contact or terminal 20 enables the connector 10 toachieve much greater co-planarity as will be described.

One of the unique features of the combined contacts or terminals 20 andfusible members 40 is that the lower portions of the two supportportions 40 a, 40 b extend or hang down well below the end or bottom tipof the tail portion 22 of the contact or terminal 20 as seen in FIGS. 1Band 2B. As will be described below, this is an important feature forallowing the much higher coplanarity and a much more effective reflowprocess for joining the connector 10 to a substrate such as a PCB.

The intermediate portion 40 c is fixedly held in the tail portion 22 ofthe contact 20 and the opposed support portions 40 a, 40 b are disposedon opposite sides of the tail portion 22 of the contact 20 as seen inFIG. 1B. The two support portions 40 a, 40 b and the intermediateportion 40 c are preferably integral and unitary, as a result of beingformed from the same fusible member as will be described below.

Before describing the preferred process for manufacturing the connector10 shown in FIGS. 1A and 1B, a preferred construction of the contact orterminal 20 will be described with reference to FIGS. 2A and 2B.

FIG. 2A is an end view and FIG. 2B is a side view of the contact orterminal 20 according to another preferred embodiment of the presentinvention, for use with the connector 10 shown in FIGS. 1A and 1B. FIG.2A shows the contact or terminal 20 without the fusible member 40affixed thereto and FIG. 2B shows the contact or terminal 20 with thefusible member 40 affixed thereto.

The contacts or terminals 20 preferably include a contact portion 21 andthe tail portion 22 at the opposite end. In a medial portion of thecontact or terminal 20, a solder stop member 23 is preferably providedto prevent the fusible material, such as solder, from wicking up towardthe contact portion 21. The solder stop member 23 may be formed of anysuitable material such as nickel or bare copper alloy. Otheranti-wicking agents like resist films or any other non-solder wettablematerial like flourine resist may also be used. In addition, the medialportion of the contact or terminal 20 preferably includes wings 24 forengaging the bottom of the core of the connector body 12 in order tomaintain a consistent distance between the tail portion 22 of thecontact or terminal 20 and the connector body 12.

The medial portion of the contact or terminal 20 may also preferablyinclude wedges 25 for engaging a side wall of a core in order to fix theposition of the contact or terminal 20 and retain the contact orterminal 20 in the core of the connector body 12. The wedges 25 fix thecontact or terminal 20 in the core in the width direction of theconnector body 12 so as to prevent stress from being applied in a lengthdirection of the connector body 12 so as to prevent problems withco-planarity.

The medial portion of the contact 20 also preferably includes lead-insor chamfers 26 which are formed by coined edges which facilitateinsertion of the contacts or terminals 20 into the cores of theconnector body 12. Each of the contacts or terminals 20 furtherpreferably includes a bump 27 for positioning and stabilizing thecontact or terminal 20 in a desired position and orientation relative tothe connector body 12.

The contact or terminal 20 also preferably includes a key hole 28 at thetail portion 22. The key hole 28 has a unique configuration that servesa special function as will be described. The key hole 28 is preferablydefined by one horizontally extending arc portion 28 a and twovertically extending arc portions 28 b disposed opposite to each other.The arc portions 28 a and 28 b cut out of the tail portion form tworetaining arms 28 c, 28 d. The tips of the two retaining arms 28 c, 28 dare preferably beveled so as to eliminate debris from the fusible member40 during the manufacture of the contact or terminal 20. Morespecifically, the tips of the tail portion 22 at the retaining arms 28 cand 28 d are preferably coined to a chamfered tip at the surfaces belowthe dotted lines on the retaining arms 28 c and 28 d. This is tofacilitate the insertion and pushing through of the fusible member 40into the keyhole 28, and prevents the retaining arms 28 c, 28 d fromremoving or displacing portions of the fusible member 40 that couldbuild up at the tail portion 22 or more specifically, at the tworetaining arms 28 c, 28 d.

FIG. 2B shows a side view of the contact or terminal 20 of FIG. 2A witha fusible member 40 being affixed thereto as will be described in moredetail below. As seen in FIG. 2B, the lower portion of the supportportions 40 a, 40 b extend down well below the bottom tip of the tailportion 22 of the contact or terminal 20.

In preferred embodiments of the present invention, the distance betweenthe bottom tip of the tail portion 22 and the bottom surface of thesupport portions 40 a, 40 b is preferably in the range of about 0.004 toabout 0.014 inches. This distance between the bottom tip of the tailportion 22 and the bottom surface of the support portions 40 a, 40 ballows for the unique drop-down function of the fusible members 40 andcontacts or terminals 20. The assembly shown in FIG. 2B is before areflow process is performed during which the fusible member 40 melts.Thus, when the assembly shown in FIG. 2B is placed on a substrate, suchas a PCB, before reflow, the support portions 40 a and 40 b rest on thesubstrate and the bottom tip of the tail portion 22 is spaced from thesubstrate by about 0.004 to about 0.014 inches. During the reflowprocess, the fusible material from support portions 40 a, 40 b wicks upthe tail portion 22 of the contact or terminal 20 toward the solder stopportion 23. When this happens, the portion of the support portions 40 a,40 b that previously hung below the bottom tip of the tail portion 22moves up the tail portion 22 such that there is no longer any portion ofthe fusible member 40 that hangs down below the bottom tip of the tailportion 22. As a result, each contact or terminal 20 and the entireconnector 10 is able to drop down such that the bottom tip of the tailportion 22 is located very close to the substrate and is reliablyattached to the substrate. This will be described in more detail later.

A preferred process for manufacturing and assembling the contacts orterminals 20 having the unique fusible member bearing tail portions 22will now be described with reference to FIGS. 3–4H.

As seen in FIG. 3, a plurality of contacts or terminals 20 can be formedsimultaneously and can be mass produced by stamping the contacts orterminals 20 from a suitable material such as any copper alloy. Thecontacts or terminals 20 are preferably held on a carrier strip 30 forease of assembling the fusible members 40 to the contacts or terminals20. The carrier strip 30 includes contact-holding members 36 arrangedsuch that there is a space or opening 34 between the carrier strip 30and the contacts or terminals 20. In addition, the carrier strip 30includes a plurality of holes 32 which are used to position, hold andfeed the carrier strip 30.

As seen in FIG. 4A, the carrier strip 30 including a plurality ofcontacts or terminals 20 is held in position such that a fusible member40, in this case, preferably a solder wire 49 for forming the fusiblemembers 40, can be moved into the opening 34 to a location just belowthe key hole 28 of the contacts or terminals 20. As seen in FIG. 4A, thesolder wire 49 is inserted into the opening 34 formed between thecarrier strip 30 and the contacts or terminals 20 so that the solderwire 49 can be inserted into the key hole 28. The insertion of thesolder wire 49 into the key hole 28 preferably involves a press-fittingoperation.

As seen in FIG. 4B, the solder wire 49 is moved upwardly into the keyhole 28 such that the solder wire 49 for forming the fusible member 40is press fit and held in the key hole 28 by the retaining arms 28 c and28 d. It is not necessary bend or crimp the retaining arms 28 c, 28 dtoward each other to hold the fusible member 40 because the dimensionsof the key hole 28 allow for press-fitting of the fusible member 40 intothe arc portions 28 a, 28 b of the key hole 28 at the tail portion 22.As can be seen in FIG. 4C, the solder wire 49 does not initiallycompletely fill the arc portions 28 a and 28 b.

As seen in FIG. 4D, the opposite ends of the solder wire 49 held in thetail portion 22 of the contact or terminal 20 are simultaneously pressedtoward each other by a press or ram 80 and a support 82, such that thetwo oppositely disposed support portions 40 a, 40 b are formed. The ram80 has a cut-out portion 84 which corresponds to a desired shape of thesupport portions 40 a, 40 b. The carrier strip 30 is held by apositioning pin 86 for accurate positioning of the contact or terminal20 within the press 80. This is shown in more detail in FIG. 4E. Theshape of the support portions 40 a, 40 b can be changed as desired bychanging the shape and configuration of the cut-out portion 84 of theram 80. The intermediate portion 40 c of the fusible member 40 betweenthe two support portions 40 a, 40 b is held in the arc portions 28 a, 28b of the tail portion 22 during the pressing of the two opposite ends ofthe fusible member 40. As a result of the forces applied by the press orram 80 and the support 82 to form the two support portions 40 a, 40 b,the intermediate portion 40 c is distorted so as to fill the arcportions 28 a, 28 b of the tail portion 22 as shown in FIG. 4F. Thisensures that the fusible member 40 is reliably held in the tail portion22 of the contact or terminal 20.

It is important to note in FIG. 4E that the pressing of the fusiblemember 40 in the press or ram 80 allows for highly precise control ofthe amounts of the support portions 40 a, 40 b that hang down below thebottom tip of the tail portions 22 of the contacts or terminals 20. Asseen in FIG. 4E, the support portions 40 a, 40 b are pressed against thecut-out portion 84 such that the amount of the fusible member 40extending down below the bottom tip of the tail portion 22 is preciselydetermined and formed, thereby enabling uniform assemblies of fusiblemembers 40 attached to contacts or terminals 20 to be formed. As aresult, when a connector 10, which includes such unique assemblies ofcontacts or terminals 20 having fusible members 40 attached thereto, isreflowed to a PCB 60, much greater co-planarity is achieved.

FIGS. 4G and 4H show the completion of the process for mounting thefusible member 40 in the contact or terminal 20. As seen in the detailof FIG. 4G, the resulting fusible member 40 is arranged in the contactor terminal 20 such that the two support portions 40 a, 40 b extend wellbelow the bottom tip or end of the tail portion 22. This is veryimportant for allowing for greatly increased co-planarity and ensuring areliable reflow process when the connector 10 is joined to a substratesuch as a PCB.

As is seen in the detail of FIG. 4F, the resultant fusible member 40 hasa unique shape and configuration. The intermediate portion 40 c has ashape that substantially corresponds to the shape of the key hole 28.That is, the intermediate portion 40 c includes a horizontally extendingarc portion 40 c 1, two vertically extending arc portions 40 c 2, 40 c3, and substantially rectangular end portion 40 c 4. The unique shapeand various portions 40 c 1, 40 c 2, 40 c 3 included in the intermediateportion 40 c reliably holds the fusible member 40 in the tail portion 22of the contact or terminal 20.

In addition, as seen in FIGS. 1A and 4E, the use of the ram 80 producesthe unique shape of the support portions 40 a, 40 b. As noted above, inone preferred embodiment, the support portions 40 a, 40 b preferablyinclude a substantially flattened portion on the bottom surface thereof.However, other shapes of the bottom surfaces may also be used for thebottom surfaces of the support portions 40 a, 40 b. The unique shape ofthe intermediate portion 40 c is important for reliably holding thefusible member 40 in the tail portion 22 of the contact or terminal 20,and allows for easy assembly of the fusible member 40 to the contact orterminal 20.

The unique configuration of the two support portions 40 a, 40 bincluding the lower portions hanging down from the intermediate portion40 c in relation to the bottom tips of the tail portions 22 of thecontact or terminals 20 is very important for allowing the connector todrop down, due to gravity, during the reflow process, which allows formuch higher than normal coplanarity and a much more effective reflowprocess because all of the contacts or terminals 20 are successfully andreliably reflowed and electrically connected to respective pads 62, aswill be described below. This unique drop down action is not possiblewith conventional connectors described above.

It is preferred that the distance between the bottom tip of the tailportion 22 and the bottom surface of the support portions 40 a, 40 b isin the range of about 0.004 to about 0.014 inches. The reason this rangeis selected is as follows.

When assembling the fusible member 40 on the contact or terminal 20, itis necessary to ensure that the fusible member 40 is reliably held onthe contact or terminal 20 until the reflow process is performed. Duringassembly of the fusible member 40 to the contact or terminal 20, one ofthe goals is to fill key hole 28, and especially the key hole portion 28b with the fusible material of the fusible member 40, in order toprevent the fusible member from falling off of the tail portion 22 ofthe contact or terminal 20. If the amount of the fusible member 40hanging down below the bottom tip of the tail portion 22 is greater thanabout 0.014 inches, it may not be possible to place the fusible member40 far enough into the key hole 28 to allow the key hole 28 to reliablyhold the fusible member and the fusible member 40 may fall off of thecontact or terminal 20. If the amount of the fusible member 40 hangingdown below the bottom tip of the tail portion 22 is less than about0.004 inches, the contacts or terminals 20 and the entire connector 10may not experience an adequate amount of drop, as described above, whichcould result in a lack of connection between a contact or terminal 20and a conductive pad or element on a substrate.

Once the unique construction of the contacts or terminals 20 includingthe fusible members 40 affixed thereto is completed as described above,the contacts or terminals 20 are inserted and preferably press-fit intocores of the connector body 12 to complete the connector 10. Instead ofbeing press fit in the connector body 12 as described above, the pinscan also be insert-molded.

In this manner, the fusible members 40 are easily and securely press-fitand pressed to the contacts or terminals 20 instead of being attached byreflowing a solder ball or other solder member thereto as inconventional methods, and then the contacts or terminals 20 are easilyinserted into the connector body 12. As a result, the tail portions 22of the contacts or terminals 20 may be tin-plated, if desired, whicheliminates or minimizes the gold embrittlement problems of the priorart.

FIGS. 5A, 5B, 6A, and 6B show how the connector 10 having the contactsor terminals 20 with the attached fusible members 40 described above ismounted to a substrate such as a PCB. FIGS. 5A and 5B show the connector10 placed on the PCB 60 before a reflow process is performed to join theconnector 10 to the PCB 60. As can be seen in FIGS. 5A and 5B, theconnector 10 is placed on the PCB 60 such that the two support portions40 a, 40 b of each contact or terminal 20 are placed on a respective pad62 of the PCB 60. Flux or solder paste (not shown) may be applied on thepads 62 prior to reflow for improving the connection between the contactor terminal 20 and the PCB 60.

A gap 64 exists between the connector body 12 and the PCB 60. The uniquestructure of the fusible members 40 allow for two different areas ofcontact and connection for securing each fusible member 40 to each pad62 as seen in FIG. 5A. More specifically, the two support portions 40 a,40 b are located on two different, spaced portions of a respective pad62. This increases the area of contact between the fusible member 40 andthe pad 62, and enables each contact or terminal 20 to be reliably andsecurely connected, both mechanically and electrically, to therespective pad 62. Thus, by increasing the area of contact between thefusible member 40 and the pad 62, a stronger solder joint is ensured.

When the connector 10 is placed on the PCB 60 before the reflow processas shown in FIG. 5A, the support members 40 a, 40 b allow the fusiblemembers to rest on the PCB 60. Because the fusible members 40 arereliably connected to the contacts or terminals 20 via press-fitting andpressing to form the support members 40 a, 40 b and the intermediateportion 40 c as described above, a reflow step for connecting thefusible members 40 to the contacts or terminals 20 is not required, asis conventionally necessary with BGA connectors. In addition, becausethe lower portions of fusible members 40 hang down well below the tip ofthe tail portion 22 of the contacts or terminals 20, a large portion ofthe contact or terminal 20 extends outside of the connector housing 12which increases the ability of the contacts or terminals 20 to flex andendure thermal cycling and other forces applied to the connector 10without experiencing any problems. Thus, the area of the solder jointformed between the contacts or terminals 20 and the PCB pads 62 via thefusible members 40 is much greater and has a greater ability to flex andwithstand forces applied thereto. In addition, because the contacts orterminals 20 are formed by stamping and the fusible member 40 isforce-fit and compressed to be joined to the contact or terminal 20, thecontacts or terminals 20 having the fusible members 40 joined theretocan be formed much more easily and accurately. As a result, when thecontacts or terminals 20 with the fusible members 40 are inserted intothe connector body 12, the distance from the connector body 12 to thetips of the tail portions 22 of the fusible members 40 is uniform forall of the contacts or terminals 20 which allows for the highercoplanarity achieved by preferred embodiments of the present invention.

FIGS. 6A and 6B show the connector 10 and PCB 60 after a reflow processhas been performed. During the reflow process, the support portions 40a, 40 b and intermediate portion 40 c melt. The fusible material fromthe intermediate portion 40 c completely fills any remaining small voidsin the key hole 28 of the tail portion 22 thereby reinforcing themounting of the fusible member 40 to the contact or terminal 20 andthereby increasing the strength of the resulting solder joint. Thefusible material of the two support portions 40 a, 40 b located belowthe intermediate portion 40 c wicks upward along the tail portion 22 ofthe contact 20 allowing the two support members 40 a, 40 b to be secureddirectly on the PCB pads 62. During the reflow process, because of thefusible members 40 being press-fit to the tail portions 22 of thecontact or terminals 20 and the fusible members 40 a, 40 b extendingbelow the tail portions 22, the connector 10 and contacts or terminals20 drop down such that the contacts or terminals 20 are located muchcloser to the PCB pads 62.

As can be seen in FIG. 6B, all of the terminals or terminals 20 arereliably connected to the pads 62 of the PCB 60 via the solder jointsformed by the two support portions 40 a, 40 b of the fusible member 40because of the increased effectiveness of the reflow process due to theunique configuration of the contacts or terminals 20 and fusible members40.

FIGS. 7A and 7B show views of a conventional connector prior to thereflow process in FIG. 7A and after the reflow process in FIG. 7B. Asseen in FIG. 7A, the connector body 12 has bowed or flexed such thatmany of the contacts or terminals 20 are spaced from the pads 62 on thePCB 60. This bowing or flexing of the connector 10 can be caused by (1)bowing or flexing that may occur during molding of the connector body12; (2) stress being relieved during either or both of the two separatereflow steps required with the prior art connector; (3) stress appliedwhen press-fitting the contacts into the housing; and (4) manufacturingtolerances. As seen in FIG. 7A, when the connector body 12 is bowed orflexed, many of the contacts or terminals 20 are unevenly spaced fromthe PCB 60 before the reflow step.

Even after reflow has been performed, as seen in FIG. 7B, many of thecontacts or terminals 20 are spaced a distance S from pads 62 on the PCB60 such that many of the contacts or terminals 20 are not connected tothe pads 62 on the PCB 60. Thus, the co-planarity and electricalconnections provided by the solder joint are very poor in the connectorshown in FIGS. 7A and 7B.

FIGS. 8A and 8B are similar figures to FIGS. 7A and 7B, but show how apreferred embodiment of the present invention is connected to a PCB 60and overcomes the problems with the connector shown in FIGS. 7A and 7B.As seen in FIG. 8A, the connector body 12 has bowed and distorted priorto reflow (FIG. 8A) in a manner similar to the conventional connectorshown in FIG. 7A. Despite the presence of a bowed or flexed connectorbody 12, after the reflow process has been performed in FIG. 8B, each ofthe contacts or terminals 20 are reliably connected to pads 62 on thePCB 60 after reflow despite the bowing and flexing of the connector body12.

As seen by comparing the results shown in FIGS. 7B and 8B, the connector10 according to preferred embodiments of the higher co-planarity and amuch more reliable reflow process, and eliminates the problems withcontacts or terminals 20 not being connected to the respectiveconductive elements on the substrate 60.

Although the connector 10 shown in FIGS. 1–6B is preferably aboard-to-board mezzanine type connector, the present invention is notlimited thereto.

The present invention can also be applied to other types of connectorsincluding a single-ended array connector 10′ or differential pair arrayconnector 10′ shown in FIG. 9, an edge card wafer 10″ for use in abackplane connector as shown in FIG. 10, or a socket connector 10′″ foruse with an IC chip such as a microprocessor chip (e.g., a Pentium®socket connector) shown in FIGS. 11 a and 11 b.

It is possible to use standoffs, for example, element 90 shown in FIG.9, to maintain desired spacing between the connector and PCB. Anotheradvantage of using the standoff 90 is the standoff reduces the stressapplied at the solder joint between the contacts 20 and the pads 62 onthe PCB 60.

According to preferred embodiments of the present invention, the uniquefusible member bearing contacts provided in the connector provide manyadvantages not achieved by conventional devices and overcome manyproblems not solved or recognized by the prior art.

The connector having the unique fusible member bearing contacts allowsfor greater co-planarity and a more reliable reflow process. Also, themanufacturing process of the connector according to preferredembodiments of the present invention is much easier, cheaper andreliable since no special equipment is required, a reflow step iseliminated, the contact or terminal does not require a right-angleportion at the tail to hold the fusible member, and the connectorhousing does not require special features in the connector body forlocating and holding solder balls.

Furthermore, the method of attaching the fusible members to the contactsor terminals via the intermediate portion fitting in the unique key holeof the tail portions of the contacts or terminals and the uniqueconstruction of the two spaced opposed support portions being seated ona conductive pad or other attachment member, increases the strength ofthe solder joint, allows the contacts or terminals to be located muchcloser to the board or substrate upon which the connector is mounted,and allows the contacts or terminals to absorb more stress and flex moreto avoid problems experienced by conventional connectors since thecontacts or terminals are not rigidly held in the insulating body of theconnector and are largely exposed from the insulating body.

As a result, the overall height of the connector according to preferredembodiments of the present invention is more controllable and evenallows for flattening of the field of contacts with a flat rigidsurface, if desired, which is not possible with BGA connectors withoutcompromising the solder joint. Furthermore, the plastic or insulatingconnector body can be spaced farther from the solder joint which allowsfor better air flow below the connector. In addition, the problems withgold embrittlement, solder wicking and solder joint weakness areeliminated or reduced in the connector according to preferredembodiments of the present invention.

It should be noted that the preferred method of attaching the fusiblemembers to the tails of the contacts or terminals has been describedabove. However, it is possible within the present invention to usealternative methods of attaching the fusible members to the contacts. Inaddition, the form, shape and arrangement of the support members can bechanged as desired.

It should be understood that the foregoing description is onlyillustrative of the present invention. Various alternatives andmodifications can be devised by those skilled in the art withoutdeparting from the present invention. Accordingly, the present inventionis intended to embrace all such alternatives, modifications andvariances which fall within the scope of the appended claims.

1. A contact for use with an electrical connector, the contactcomprising: a contact portion located at a first end of the contact; atail portion located at a second end of the contact; and a fusiblemember attached to the tail portion and including an intermediateportion and two support members disposed on opposite sides of theintermediate portion, and the two support members extend below the tailportion of the contact; wherein the two support members are arranged tomove along the tail portion of the contact in a direction toward aconnector body during a reflow process to allow the tail portion of thecontact to drop down in a direction toward a substrate upon which thecontact is to be mounted.
 2. The contact according to claim 1, whereineach of the two support members extends below the tail portion of thecontact by a distance of about 0.004 inches to about 0.014 inches. 3.The contact according to claim 1, wherein an outer periphery of each ofthe two support members is greater than an outer periphery of the tailportion of the contact.
 4. The contact according to claim 1, whereineach of the two support members has one of a substantially flat bottomsurface, a substantially rounded bottom surface, a substantiallyspherical bottom surface, a substantially conical bottom surface, asubstantially rectangular bottom surface and a substantially squarebottom surface.
 5. The contact according to claim 1, wherein the tailportion is substantially straight and does not include a right angleportion.
 6. The contact according to claim 1, further comprising wingsfor engaging a core of a connector body to maintain a uniform distancebetween the tail portion of the contact and the connector body.
 7. Thecontact according to claim 1, further comprising wedges for engaging aside wall of a core of a connector body in order to fix the contact inthe connector body.
 8. The contact according to claim 1, furthercomprising lead-in portions having coined edges arranged to position thecontact in a connector body.
 9. The contact according to claim 1,further comprising bumps for positioning the contact within a connectorbody.
 10. The contact according to claim 1, wherein the intermediateportion and the two support members are integral and unitary.
 11. Thecontact according to claim 1, wherein the two support members arelocated on opposite sides of the tail portion of the contact.
 12. Thecontact according to claim 1, wherein each of the two support membersextends from the intermediate portion and are larger than theintermediate portion.
 13. The contact according to claim 1, wherein thecontact is made of a copper alloy.
 14. The contact according to claim 1,wherein the tail portion includes two retaining arms holding the fusiblemember.
 15. The contact according to claim 14, wherein each of the tworetaining arms has a chamfered tip.
 16. A contact for use with anelectrical connector, the contact comprising: a contact portion locatedat a first end of the contact; a tail portion located at a second end ofthe contact; and a fusible member attached to the tail portion andincluding an intermediate portion and two support members disposed onopposite sides of the intermediate portion, and the two support membersextend below the tail portion of the contact; wherein the tail portionincludes a key hole defined by a first horizontally extending arc andtwo vertically extending arcs.
 17. The contact according to claim 16,wherein the intermediate portion is fitted within the key hole.
 18. Thecontact according to claim 16, wherein the intermediate portion fillsthe keyhole defined by the first horizontally extending arc and the twovertically extending arcs.
 19. The contact according to claim 16,wherein each of the two support members extends below the tail portionof the contact by a distance of about 0.004 inches to about 0.014inches.
 20. The contact according to claim 16, wherein an outerperiphery of each of the two support members is greater than an outerperiphery of the tail portion of the contact.
 21. The contact accordingto claim 16, wherein each of the two support members has one of asubstantially flat bottom surface, a substantially rounded bottomsurface, a substantially spherical bottom surface, a substantiallyconical bottom surface, a substantially rectangular bottom surface and asubstantially square bottom surface.
 22. The contact according to claim16, wherein the tail portion is substantially straight and does notinclude a right angle portion.
 23. The contact according to claim 16,further comprising wings for engaging a core of a connector body tomaintain a uniform distance between the tail portion of the contact andthe connector body.
 24. The contact according to claim 16, furthercomprising wedges for engaging a side wall of a core of a connector bodyin order to fix the contact in the connector body.
 25. The contactaccording to claim 16, further comprising lead-in portions having coinededges arranged to position the contact in a connector body.
 26. Thecontact according to claim 16, further comprising bumps for positioningthe contact within a connector body.
 27. The contact according to claim16, wherein the intermediate portion and the two support members areintegral and unitary.
 28. The contact according to claim 16, wherein thetwo support members are located on opposite sides of the tail portion ofthe contact.
 29. The contact according to claim 16, wherein each of thetwo support members extends from the intermediate portion and are largerthan the intermediate portion.
 30. The contact according to claim 16,wherein the contact is made of a copper alloy.
 31. The contact accordingto claim 16, wherein the tail portion includes two retaining armsholding the fusible member.
 32. The contact according to claim 31,wherein each of the two retaining arms has a chamfered tip.
 33. Acontact for use with an electrical connector, the contact comprising: acontact portion located at a first end of the contact; a tail portionlocated at a second end of the contact; a fusible member attached to thetail portion and including an intermediate portion and two supportmembers disposed on opposite sides of the intermediate portion, and thetwo support members extend below the tail portion of the contact; amedial portion located between the tail portion and the contact portion;and a solder stop portion located at the medial portion of the contact.34. The contact according to claim 33, wherein each of the two supportmembers extends below the tail portion of the contact by a distance ofabout 0.004 inches to about 0.014 inches.
 35. The contact according toclaim 33, wherein an outer periphery of each of the two support membersis greater than an outer periphery of the tail portion of the contact.36. The contact according to claim 33, wherein each of the two supportmembers has one of a substantially flat bottom surface, a substantiallyrounded bottom surface, a substantially spherical bottom surface, asubstantially conical bottom surface, a substantially rectangular bottomsurface and a substantially square bottom surface.
 37. The contactaccording to claim 33, wherein the tail portion is substantiallystraight and does not include a right angle portion.
 38. The contactaccording to claim 33, further comprising wings for engaging a core of aconnector body to maintain a uniform distance between the tail portionof the contact and the connector body.
 39. The contact according toclaim 33, further comprising wedges for engaging a side wall of a coreof a connector body in order to fix the contact in the connector body.40. The contact according to claim 33, further comprising lead-inportions having coined edges arranged to position the contact in aconnector body.
 41. The contact according to claim 33, furthercomprising bumps for positioning the contact within a connector body.42. The contact according to claim 33, wherein the intermediate portionand the two support members are integral and unitary.
 43. The contactaccording to claim 33, wherein the two support members are located onopposite sides of the tail portion of the contact.
 44. The contactaccording to claim 33, wherein each of the two support members extendsfrom the intermediate portion and are larger than the intermediateportion.
 45. The contact according to claim 33, wherein the contact ismade of a copper alloy.
 46. The contact according to claim 33, whereinthe tail portion includes two retaining arms holding the fusible member.47. The contact according to claim 46, wherein each of the two retainingarms has a chamfered tip.